This is one of the big headaches for Google: Although it builds the operating system, it has no control over when it actually makes its way onto users smartphones. It's up to the handset manufacturers to push out updates to their users — meaning it can take an age for the latest innovations and features to reach the general public.

Developers end up working a version or two behind the current OS. Right now, the biggest version of Android currently in use is KitKat — which was launched all the way back in 2013. It has 36.1% market share, followed by Lollipop, its successor, with 32.6%.

Google

However, this model — giving the OS away for free for anyone to include in their phones — does allow Android to scale massively. "We have something like 400 OEM partners ... 4,000 different types of device ... the last number of active users is about 1 billion," Google's head of Android engineering, Andrei Popescu, told Business Insider in September 2015. "I think this model has served us pretty well."

Mark Bennett, head of Google Play in Europe, says that "definitely, if you look in the past [the fragmentation] was a really big issue." But he points to the array of tools Google now offers developers to mitigate this "differentiated market" — particularly the Cloud Test Lab, a tool for testing apps on different Android handsets to maximise compatibility. "Developer-first mentality permeates through everything we do."

That said, it's a radically different approach to Apple's iOS, which sees skyhigh adoption rates. The most recent version, iOS 9, found its way onto 66% of all iOS devices within 2 months of its launch in September 2015.